Hi everyone, I'm new to the forum and new to saltwater tanks. I just added a cleaning crew 2 weeks ago and I've noticed that the crab shells have been loosing their color and turing a lighter color around the tips. It started a week ago. All my water parameters are within normal limits including Ca. Anyone have an ideas what it could be? Thank you for your input.

Well, although I'm on my fine in the sun and pics are hard to see, I'd say those are dead snail shells. See as how they're new in your tank, there is undoubtedly different lighting and chemical balances between what you hot and where they came from.
Just make sure you have an ample supply of new dead shells for when the hermits want to move to a new house, or grow a bit